High temperature super-conducting transformers (HTS), e.g., those operating in the temperature ranges of −487° F. (−253° C.) to −385° F. (−196° C.), are relatively new when compared to conventional oil-filled transformers. HTS transformers are revolutionary in that they use high temperature super-conducting materials instead of copper windings to transform voltage levels.
In transforming a voltage supply from one voltage level to another voltage level, heat is generated within the transformer. In conventional oil-filled transformers oil is circulated through the transformer to transfer heat from the copper windings to the oil. The oil is then returned to a radiator where it is cooled.
However, in conventional oil-filled transformers, the oil is not only utilized as a material for heat transfer, but also as a dielectric material to prevent current from flowing between two components or parts of the transformer that are at different potentials. The use of oil as a dielectric medium is important because without the oil there is a potential for the occurrence of flashovers that could lead to failures in the performance of the transformer. A flashover involves an electiric arc or spark, i.e., the flow of current, between two components of different potentials when the dielectric material between the two components breaks down and conducts current.
However, oil is not needed in HTS transformers and HTS transformers can operate in low conductivity vacuum environments. Thus, because HTS transformers do not require oil, HTS transformers can be made smaller and lighter than conventional oil-filled transformers. In addition, HTS transformers can be placed in environments where conventional oil-filled transformers would not traditionally be placed.
In HTS transformers, super-conducting materials are utilized, rather than the copper windings, to transform a voltage supply from one level to another. An impressive characteristic of super-conducting materials is that they are able to conduct current with almost no resistance. Thus, super-conducting materials generate less heat than conventional oil-filled transformers.
A disadvantage of HTS transformers is that the dielectric strength of a vacuum is less than the dielectric strength of oil. Thus, conventional methods of constructing HTS transformers, which rely on oil being utilized as a dielectric between components of different voltage potentials, are not always suitable for HTS transformers because oil is not present.
For example, the method for constructing the interconnect system of conventional oil filled transformers is not suitable for HTS transformers. The interconnect system of transformers includes the electrical connections between the leads of the coil sets of the transformer to establish the phases of the transformer. In addition the interconnect system may include electrical connections between the high voltage leads from a power supply and the leads from the coil sets.
In conventional oil-filled transformers, the leads from the inputs and outputs of the coil sets may be at different voltage potentials from other components within the transformer. Further, the high voltage leads brought into the transformer may be at a different potential than the leads from the coil sets. However, the presence of oil in conventional oil-filled transformers helps to prevent flashover that may occur between transformer components at different voltage potentials. Further, there is sufficient space within the transformer to establish adequate dielectric clearances, i.e., a minimum distance between two objects to prevent flashover. Consequently, transformer failures are reduced and the lifetime of the transformer is extended.
However, the components of HTS transformers function within a vacuum environment and the dielectric strength of the vacuum environment is not as strong as an oil-filled environment. Further, cooling devices that create the −487° F. (−253° C.) to −385° F. (−196° C.) environment within HTS transformers reduce the space in HTS transformers, such that adequate dielectric clearances cannot be provided between components at different voltage potentials. Accordingly, it is desirable to provide methods and/or devices that prevent flashover within HTS transformers.
Further, it is desirable to provide methods and/or devices for connecting high voltage leads from a voltage supply to leads from HTS coil sets that avoid the occurrence of flashover.